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Buigues P, Gehrke S, Badaoui M, Dudas B, Mandana G, Qi T, Bottegoni G, Rosta E. Investigating the Unbinding of Muscarinic Antagonists from the Muscarinic 3 Receptor. J Chem Theory Comput 2023; 19:5260-5272. [PMID: 37458730 PMCID: PMC10413856 DOI: 10.1021/acs.jctc.3c00023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Indexed: 08/09/2023]
Abstract
Patient symptom relief is often heavily influenced by the residence time of the inhibitor-target complex. For the human muscarinic receptor 3 (hMR3), tiotropium is a long-acting bronchodilator used in conditions such as asthma or chronic obstructive pulmonary disease (COPD). The mechanistic insights into this inhibitor remain unclear; specifically, the elucidation of the main factors determining the unbinding rates could help develop the next generation of antimuscarinic agents. Using our novel unbinding algorithm, we were able to investigate ligand dissociation from hMR3. The unbinding paths of tiotropium and two of its analogues, N-methylscopolamin and homatropine methylbromide, show a consistent qualitative mechanism and allow us to identify the structural bottleneck of the process. Furthermore, our machine learning-based analysis identified key roles of the ECL2/TM5 junction involved in the transition state. Additionally, our results point to relevant changes at the intracellular end of the TM6 helix leading to the ICL3 kinase domain, highlighting the closest residue L482. This residue is located right between two main protein binding sites involved in signal transduction for hMR3's activation and regulation. We also highlight key pharmacophores of tiotropium that play determining roles in the unbinding kinetics and could aid toward drug design and lead optimization.
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Affiliation(s)
- Pedro
J. Buigues
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Sascha Gehrke
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Magd Badaoui
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Balint Dudas
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Gaurav Mandana
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Tianyun Qi
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
| | - Giovanni Bottegoni
- Dipartimento
di Scienze Biomolecolari (DISB), University
of Urbino, Urbino Piazza Rinascimento, 6, Urbino 61029, Italy
- Institute
of Clinical Sciences, University of Birmingham, Edgbaston, B15 2TT Birmingham, United Kingdom
| | - Edina Rosta
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United
Kingdom
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2
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Avet C, Denoyelle C, L'Hôte D, Petit F, Guigon CJ, Cohen-Tannoudji J, Simon V. GnRH regulates the expression of its receptor accessory protein SET in pituitary gonadotropes. PLoS One 2018; 13:e0201494. [PMID: 30052687 PMCID: PMC6063425 DOI: 10.1371/journal.pone.0201494] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 07/16/2018] [Indexed: 01/26/2023] Open
Abstract
Reproductive function is under the control of the neurohormone GnRH, which activates a G-protein-coupled receptor (GnRHR) expressed in pituitary gonadotrope cells. GnRHR activates a complex signaling network to regulate synthesis and secretion of the two gonadotropin hormones, luteinizing hormone and follicle-stimulating hormone, both regulating gametogenesis and steroidogenesis in gonads. Recently, in an attempt to identify the mechanisms underlying GnRHR signaling plasticity, we identified the first interacting partner of GnRHR, the proto-oncogene SET. We showed that SET binds to intracellular domains of GnRHR to enhance its coupling to cAMP pathway in αT3-1 gonadotrope cells. Here, we demonstrate that SET protein is rapidly regulated by GnRH, which increases SET phosphorylation state and decreases dose-dependently SET protein level. Our results highlight a post-translational regulation of SET protein involving the proteasome pathway. We determined that SET phosphorylation upon GnRH stimulation is mediated by PKC and that PKC mediates GnRH-induced SET down-regulation. Phosphorylation on serine 9 targets SET for degradation into the proteasome. Furthermore, a non-phosphorylatable SET mutant on serine 9 is resistant to GnRH-induced down-regulation. Altogether, these data suggest that GnRH-induced SET phosphorylation on serine 9 mediates SET protein down-regulation through the proteasome pathway. Noteworthy, SET down-regulation was also observed in response to pulsatile GnRH stimulation in LβT2 gonadotrope cells as well as in vivo in prepubertal female mice supporting its physiological relevance. In conclusion, this study highlights a regulation of SET protein by the neurohormone GnRH and identifies some of the mechanisms involved.
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Affiliation(s)
- Charlotte Avet
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - Chantal Denoyelle
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - David L'Hôte
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - Florence Petit
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - Céline J Guigon
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - Joëlle Cohen-Tannoudji
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
| | - Violaine Simon
- Sorbonne Paris Cité, Université Paris-Diderot, CNRS UMR 8251, INSERM U1133, Biologie Fonctionnelle et Adaptative, Physiologie de l'axe gonadotrope, Paris, France
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3
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Pronin AN, Wang Q, Slepak VZ. Teaching an Old Drug New Tricks: Agonism, Antagonism, and Biased Signaling of Pilocarpine through M3 Muscarinic Acetylcholine Receptor. Mol Pharmacol 2017; 92:601-612. [PMID: 28893976 DOI: 10.1124/mol.117.109678] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/06/2017] [Indexed: 12/27/2022] Open
Abstract
Pilocarpine is a prototypical drug used to treat glaucoma and dry mouth and is classified as either a full or partial muscarinic agonist. Here, we report several unexpected results pertaining to its interaction with muscarinic M3 receptor (M3R). We found that pilocarpine was 1000 times less potent in stimulating mouse-eye pupil constriction than muscarinic agonists oxotremorin-M (Oxo-M) or carbachol (CCh), although all three ligands have similar Kd values for M3R. In contrast to CCh or Oxo-M, pilocarpine does not induce Ca2+ mobilization via endogenous M3R in human embryonic kidney cell line 293T (HEK293T) or mouse insulinoma (MIN6) cells. Pilocarpine also fails to stimulate insulin secretion and, instead, antagonizes the insulinotropic effect of Oxo-M and CCh-induced Ca2+ upregulation; however, in HEK293T or Chinese hamster ovary-K1 cells overexpressing M3R, pilocarpine induces Ca2+ transients like those recorded with another cognate G protein-coupled muscarinic receptor, M1R. Stimulation of cells overexpressing M1R or M3R with CCh resulted in a similar reduction in phosphatidylinositol 4,5-bisphosphate (PIP2). In contrast to CCh, pilocarpine stimulated PIP2 hydrolysis only in cells overexpressing M1R but not M3R. Moreover, pilocarpine blocked CCh-stimulated PIP2 hydrolysis in M3R-overexpressing cells, thus, it acted as an antagonist. Pilocarpine activates extracellular regulated kinase 1/2 in MIN6 cells. The stimulatory effect on extracellular regulated kinase (ERK1/2) was blocked by the Src family kinase inhibitor PP2, indicating that the action of pilocarpine on endogenous M3R is biased toward β-arrestin. Taken together, our findings show that pilocarpine can act as either an agonist or antagonist of M3R, depending on the cell type, expression level, and signaling pathway downstream of this receptor.
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Affiliation(s)
- Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
| | - Qiang Wang
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
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4
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Alfonzo MJ, Alfonzo RGD, Alfonzo González M, de Becemberg IL. Muscarinic drugs regulate the PKG-II-dependent phosphorylation of M3 muscarinic acetylcholine receptors at plasma membranes from airway smooth muscle. J Recept Signal Transduct Res 2015; 35:319-28. [PMID: 26053513 DOI: 10.3109/10799893.2014.982826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Muscarinic agonists induce the activation of the airway smooth muscle (ASM) leading to smooth muscle contraction, important in asthma. This activation is mediated through M2/M3 muscarinic acetylcholine receptors (mAChRs). Muscarinic receptor activity, expressed as [(3)H]QNB binding at plasma membranes from bovine tracheal smooth muscle (BTSM), increased with cGMP and was augmented significantly cGMP plus ATP but diminished with the PKG-II inhibitor, Sp-8-pCPT-cGMPS. The [(3)H]-QNB binding was accelerated by okadaic acid, (OKA), a protein phosphatase (PPase) inhibitor. These two results indicated the involvement of a membrane-bound PPase. Moreover, a cGMP-dependent-[(32)P]γATP phosphorylation of plasma membranes from BTSM was stimulated at low concentrations of muscarinic agonist carbamylcholine (CC). However, higher amounts of CC produced a significant decrement of [(32)P]-labeling. A selective M3mAChR antagonist, 4-DAMP produced a dramatic inhibition of the basal and CC-dependent [(32)P]-labeling. The [(32)P] labeled membrane sediments were detergent solubilized and immunoprecipitated with specific M2/M3mAChR antibodies. The M3mAChR immuno-precipitates exhibited the highest cGMP-dependent [(32)P]-labeling, indicating it is a PKG-II substrate. Experiments using synthetic peptides from the C-terminal of the third intracellular loop (i3) of both M2mAChR (356-369) and M3mAChR (480-493) as external PKG-II substrates resulted in the i3M3-peptide being heavily phosphorylated. These results indicated that PKG-II phosphorylated the M3mAChR at the i3M3 domain ((480)MSLIKEKK(485)), suggesting that Ser(481) may be the target. Finally, this phosphorylation site seems to be regulated by a membrane-bound PPase linked to muscarinic receptor. These findings are important to understand the role of M3mAChR in the patho-physiology of ASM involved in asthma and COPD.
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Affiliation(s)
- Marcelo J Alfonzo
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Ramona González de Alfonzo
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Marcelo Alfonzo González
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Itala Lippo de Becemberg
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
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5
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Karpinsky-Semper D, Tayou J, Levay K, Schuchardt BJ, Bhat V, Volmar CH, Farooq A, Slepak VZ. Helix 8 and the i3 loop of the muscarinic M3 receptor are crucial sites for its regulation by the Gβ5-RGS7 complex. Biochemistry 2015; 54:1077-88. [PMID: 25551629 PMCID: PMC4318586 DOI: 10.1021/bi500980d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
![]()
The muscarinic M3 receptor (M3R)
is a Gq-coupled receptor and is
known to interact with many intracellular regulatory proteins. One
of these molecules is Gβ5-RGS7, the permanently associated heterodimer
of G protein β-subunit Gβ5 and RGS7, a regulator of G
protein signaling. Gβ5-RGS7 can attenuate M3R-stimulated release
of Ca2+ from intracellular stores or enhance the influx
of Ca2+ across the plasma membrane. Here we show that deletion
of amino acids 304–345 from the central portion of the i3 loop
renders M3R insensitive to regulation by Gβ5-RGS7. In addition
to the i3 loop, interaction of M3R with Gβ5-RGS7 requires helix
8. According to circular dichroism spectroscopy, the peptide corresponding
to amino acids 548–567 in the C-terminus of M3R assumes an
α-helical conformation. Substitution of Thr553 and Leu558 with
Pro residues disrupts this α-helix and abolished binding to
Gβ5-RGS7. Introduction of the double Pro substitution into full-length
M3R (M3RTP/LP) prevents trafficking of the receptor to
the cell surface. Using atropine or other antagonists as pharmacologic
chaperones, we were able to increase the level of surface expression
of the TP/LP mutant to levels comparable to that of wild-type M3R.
However, M3R-stimulated calcium signaling is still severely compromised.
These results show that the interaction of M3R with Gβ5-RGS7
requires helix 8 and the central portion of the i3 loop.
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Affiliation(s)
- Darla Karpinsky-Semper
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine , 1600 NW 10th Avenue, RMSB6024A, Miami, Florida 33136, United States
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6
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The C. elegans VIG-1 and FRM-1 modulate carbachol-stimulated ERK1/2 activation in chinese hamster ovary cells expressing the muscarinic acetylcholine receptor GAR-3. Neurochem Res 2014; 39:777-84. [PMID: 24604007 DOI: 10.1007/s11064-014-1268-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/19/2014] [Accepted: 02/25/2014] [Indexed: 01/22/2023]
Abstract
Many neurotransmitter receptors are known to interact with a variety of intracellular proteins that modulate signaling processes. In an effort to understand the molecular mechanism by which acetylcholine (ACh) signaling is modulated, we searched for proteins that interact with GAR-3, the Caenorhabditis elegans homolog of muscarinic ACh receptors. We isolated two proteins, VIG-1 and FRM-1, in a yeast two-hybrid screen of a C. elegans cDNA library using the third intracellular (i3) loop of GAR-3 as bait. To test whether these proteins regulate ACh signaling, we utilized Chinese hamster ovary (CHO) cells stably expressing GAR-3 (GAR-3/CHO cells). Previously we have shown that the cholinergic agonist carbachol stimulates extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in an atropine-sensitive manner in this cell line. When VIG-1 was transiently expressed in GAR-3/CHO cells, carbachol-stimulated ERK1/2 activation was substantially reduced. In contrast, transient expression of FRM-1 significantly enhanced carbachol-stimulated ERK1/2 activation. Neither VIG-1 nor FRM-1 expression appeared to alter the affinity between GAR-3 and carbachol. In support of this notion, expression of these proteins did not affect GAR-3-mediated phospholipase C activation. To verify the modulation of ERK1/2 activity by VIG-1 and FRM-1, we used an i3 loop deletion mutant of GAR-3 (termed GAR-3Δi3). Carbachol treatment evoked robust ERK1/2 activation in CHO cells stably expressing the deletion mutant (GAR-3Δi3/CHO cells). However, transient expression of either VIG-1 or FRM-1 had little effect on carbachol-stimulated ERK1/2 activation in GAR-3Δi3/CHO cells. Taken together, these results indicate that VIG-1 and FRM-1 regulate GAR-3-mediated ERK1/2 activation by interacting with the i3 loop of GAR-3.
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7
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Chaker S, Kashat L, Voisin S, Kaur J, Kak I, MacMillan C, Ozcelik H, Michael Siu KW, Ralhan R, Walfish PG. Secretome proteins as candidate biomarkers for aggressive thyroid carcinomas. Proteomics 2013; 13:771-87. [DOI: 10.1002/pmic.201200356] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 11/15/2012] [Accepted: 12/10/2012] [Indexed: 12/28/2022]
Affiliation(s)
- Seham Chaker
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
| | - Lawrence Kashat
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
| | - Sebastien Voisin
- Department of Chemistry and Centre for Research in Mass Spectrometry; York University; Toronto ON Canada
| | - Jatinder Kaur
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
| | - Ipshita Kak
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
| | - Christina MacMillan
- Department of Pathology & Laboratory Medicine; Mount Sinai Hospital; Toronto ON Canada
| | - Hilmi Ozcelik
- Samuel Lunenfeld Research Institute; Mount Sinai Hospital L6-303; Toronto ON Canada
| | - K. W. Michael Siu
- Department of Chemistry and Centre for Research in Mass Spectrometry; York University; Toronto ON Canada
| | - Ranju Ralhan
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
- Department of Pathology & Laboratory Medicine; Mount Sinai Hospital; Toronto ON Canada
- Joseph and Mildred Sonshine Family Centre for Head and Neck Diseases; Department of Otolaryngology-Head and Neck Surgery Program; Mount Sinai Hospital; Toronto ON Canada
- Department of Otolaryngology-Head and Neck Surgery; University of Toronto; Toronto ON Canada
| | - Paul G. Walfish
- Alex and Simona Shnaider Laboratory in Molecular Oncology; Samuel Lunenfeld Research Institute; Mount Sinai Hospital; Toronto ON Canada
- Institute of Medical Science; University of Toronto; Toronto ON Canada
- Department of Pathology & Laboratory Medicine; Mount Sinai Hospital; Toronto ON Canada
- Joseph and Mildred Sonshine Family Centre for Head and Neck Diseases; Department of Otolaryngology-Head and Neck Surgery Program; Mount Sinai Hospital; Toronto ON Canada
- Department of Medicine; Endocrine Division; Mount Sinai Hospital and University of Toronto Medical School; Toronto ON Canada. Department of Otolaryngology-Head and Neck Surgery; University of Toronto; Toronto ON Canada
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8
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Avet C, Garrel G, Denoyelle C, Laverrière JN, Counis R, Cohen-Tannoudji J, Simon V. SET protein interacts with intracellular domains of the gonadotropin-releasing hormone receptor and differentially regulates receptor signaling to cAMP and calcium in gonadotrope cells. J Biol Chem 2012; 288:2641-54. [PMID: 23233674 DOI: 10.1074/jbc.m112.388876] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In mammals, the receptor of the neuropeptide gonadotropin-releasing hormone (GnRHR) is unique among the G protein-coupled receptor (GPCR) family because it lacks the carboxyl-terminal tail involved in GPCR desensitization. Therefore, mechanisms involved in the regulation of GnRHR signaling are currently poorly known. Here, using immunoprecipitation and GST pull-down experiments, we demonstrated that SET interacts with GnRHR and targets the first and third intracellular loops. We delineated, by site-directed mutagenesis, SET binding sites to the basic amino acids (66)KRKK(69) and (246)RK(247), located next to sequences required for receptor signaling. The impact of SET on GnRHR signaling was assessed by decreasing endogenous expression of SET with siRNA in gonadotrope cells. Using cAMP and calcium biosensors in gonadotrope living cells, we showed that SET knockdown specifically decreases GnRHR-mediated mobilization of intracellular cAMP, whereas it increases its intracellular calcium signaling. This suggests that SET influences signal transfer between GnRHR and G proteins to enhance GnRHR signaling to cAMP. Accordingly, complexing endogenous SET by introduction of the first intracellular loop of GnRHR in αT3-1 cells significantly reduced GnRHR activation of the cAMP pathway. Furthermore, decreasing SET expression prevented cAMP-mediated GnRH stimulation of Gnrhr promoter activity, highlighting a role of SET in gonadotropin-releasing hormone regulation of gene expression. In conclusion, we identified SET as the first direct interacting partner of mammalian GnRHR and showed that SET contributes to a switch of GnRHR signaling toward the cAMP pathway.
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Affiliation(s)
- Charlotte Avet
- Université Paris Diderot, Sorbonne Paris Cité, Biologie Fonctionnelle et Adaptative, Equipe Physiologie de l'Axe Gonadotrope, Case Courrier 7007, CNRS-EAC 4413, 4 Rue MA Lagroua Weill Hallé, 75013 Paris, France
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9
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Simon V, Oner SS, Cohen-Tannoudji J, Tobin AB, Lanier SM. Influence of the accessory protein SET on M3 muscarinic receptor phosphorylation and G protein coupling. Mol Pharmacol 2012; 82:17-26. [PMID: 22466417 DOI: 10.1124/mol.111.075523] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The proto-oncogene and inhibitor of protein phosphatase 2A (PP2A), SET, interacts with the third intracellular loop of the M3 muscarinic receptor (M3-MR), and SET knockdown with small interfering RNA (siRNA) in Chinese hamster ovary (CHO) cells augments M3-MR signaling. However, the mechanism of this action of SET on receptor signaling has not been defined, and we initiated studies to address this question. Knockdown of SET by siRNA in CHO cells stably expressing the M3-MR did not alter agonist-induced receptor phosphorylation or receptor internalization. Instead, it increased the extent of receptor dephosphorylation after agonist removal by ∼60%. In competition binding assays, SET knockdown increased high-affinity binding of agonist in intact cells and membrane preparations. Glutathione transferase pull-down assays and site-directed mutagenesis revealed a SET binding site adjacent to and perhaps overlapping the G protein-binding site within the third intracellular loop of the receptor. Mutation of this region in the M3-MR altered receptor coupling to G protein. These data indicate that SET decreases M3-MR dephosphorylation and regulates receptor engagement with G protein, both of which may contribute to the inhibitory action of SET on M3-MR signaling.
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Affiliation(s)
- Violaine Simon
- University Paris Diderot, Sorbonne Paris Cité, Biologie Fonctionnelle et Adaptative, Centre National de la Recherche Scientifique-Equipe d’Accueil Conventionée 4413, Paris, France
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10
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Vasudevan NT, Mohan ML, Gupta MK, Hussain AK, Naga Prasad SV. Inhibition of protein phosphatase 2A activity by PI3Kγ regulates β-adrenergic receptor function. Mol Cell 2011; 41:636-48. [PMID: 21419339 DOI: 10.1016/j.molcel.2011.02.025] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/18/2010] [Accepted: 02/23/2011] [Indexed: 01/08/2023]
Abstract
Phosphoinositide 3-kinase γ (PI3Kγ) is activated by G protein-coupled receptors (GPCRs). We show here that PI3Kγ inhibits protein phosphatase 2A (PP2A) at the β-adrenergic receptor (βAR, a GPCR) complex altering G protein coupling. PI3Kγ inhibition results in significant increase of βAR-associated phosphatase activity leading to receptor dephosphorylation and resensitization preserving cardiac function. Mechanistically, PI3Kγ inhibits PP2A activity at the βAR complex by phosphorylating an intracellular inhibitor of PP2A (I2PP2A) on serine residues 9 and 93, resulting in enhanced binding to PP2A. Indeed, enhanced phosphorylation of β2ARs is observed with a phosphomimetic I2PP2A mutant that was completely reversed with a mutant mimicking dephosphorylated state. siRNA depletion of endogenous I2PP2A augments PP2A activity despite active PI3K resulting in β2AR dephosphorylation and sustained signaling. Our study provides the underpinnings of a PI3Kγ-mediated regulation of PP2A activity that has significant consequences on receptor function with broad implications in cellular signaling.
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Affiliation(s)
- Neelakantan T Vasudevan
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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11
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Kendall RT, Strungs EG, Rachidi SM, Lee MH, El-Shewy HM, Luttrell DK, Janech MG, Luttrell LM. The beta-arrestin pathway-selective type 1A angiotensin receptor (AT1A) agonist [Sar1,Ile4,Ile8]angiotensin II regulates a robust G protein-independent signaling network. J Biol Chem 2011; 286:19880-91. [PMID: 21502318 DOI: 10.1074/jbc.m111.233080] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The angiotensin II peptide analog [Sar(1),Ile(4),Ile(8)]AngII (SII) is a biased AT(1A) receptor agonist that stimulates receptor phosphorylation, β-arrestin recruitment, receptor internalization, and β-arrestin-dependent ERK1/2 activation without activating heterotrimeric G-proteins. To determine the scope of G-protein-independent AT(1A) receptor signaling, we performed a gel-based phosphoproteomic analysis of AngII and SII-induced signaling in HEK cells stably expressing AT(1A) receptors. A total of 34 differentially phosphorylated proteins were detected, of which 16 were unique to SII and eight to AngII stimulation. MALDI-TOF/TOF mass fingerprinting was employed to identify 24 SII-sensitive phosphoprotein spots, of which three (two peptide inhibitors of protein phosphatase 2A (I1PP2A and I2PP2A) and prostaglandin E synthase 3 (PGES3)) were selected for validation and further study. We found that phosphorylation of I2PP2A was associated with rapid and transient inhibition of a β-arrestin 2-associated pool of protein phosphatase 2A, leading to activation of Akt and increased phosphorylation of glycogen synthase kinase 3β in an arrestin signalsome complex. SII-stimulated PGES3 phosphorylation coincided with an increase in β-arrestin 1-associated PGES3 and an arrestin-dependent increase in cyclooxygenase 1-dependent prostaglandin E(2) synthesis. These findings suggest that AT(1A) receptors regulate a robust G protein-independent signaling network that affects protein phosphorylation and autocrine/paracrine prostaglandin production and that these pathways can be selectively modulated by biased ligands that antagonize G protein activation.
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Affiliation(s)
- Ryan T Kendall
- Department of Medicine, Division of Endocrinology, Diabetes, and Medical Genetics, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Duvernay MT, Wang H, Dong C, Guidry JJ, Sackett DL, Wu G. Alpha2B-adrenergic receptor interaction with tubulin controls its transport from the endoplasmic reticulum to the cell surface. J Biol Chem 2011; 286:14080-9. [PMID: 21357695 DOI: 10.1074/jbc.m111.222323] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
It is well recognized that the C terminus (CT) plays a crucial role in modulating G protein-coupled receptor (GPCR) transport from the endoplasmic reticulum (ER) to the cell surface. However the molecular mechanisms that govern CT-dependent ER export remain elusive. To address this issue, we used α(2B)-adrenergic receptor (α(2B)-AR) as a model GPCR to search for proteins interacting with the CT. By using peptide-conjugated affinity matrix combined with proteomics and glutathione S-transferase fusion protein pull-down assays, we identified tubulin directly interacting with the α(2B)-AR CT. The interaction domains were mapped to the acidic CT of tubulin and the basic Arg residues in the α(2B)-AR CT, particularly Arg-437, Arg-441, and Arg-446. More importantly, mutation of these Arg residues to disrupt tubulin interaction markedly inhibited α(2B)-AR transport to the cell surface and strongly arrested the receptor in the ER. These data provide the first evidence indicating that the α(2B)-AR C-terminal Arg cluster mediates its association with tubulin to coordinate its ER-to-cell surface traffic and suggest a novel mechanism of GPCR export through physical contact with microtubules.
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Affiliation(s)
- Matthew T Duvernay
- From the Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
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Sandiford SL, Wang Q, Levay K, Buchwald P, Slepak VZ. Molecular organization of the complex between the muscarinic M3 receptor and the regulator of G protein signaling, Gbeta(5)-RGS7. Biochemistry 2010; 49:4998-5006. [PMID: 20443543 DOI: 10.1021/bi100080p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The complex of the regulator of G protein signaling (RGS), Gbeta(5)-RGS7, can inhibit signal transduction via the M3 muscarinic acetylcholine receptor (M3R). RGS7 consists of three distinct structural entities: the DEP domain and its extension DHEX, the Ggamma-like (GGL) domain, which is permanently bound to Gbeta subunit Gbeta(5), and the RGS domain responsible for the interaction with Galpha subunits. Inhibition of the M3R by Gbeta(5)-RGS7 is independent of the RGS domain but requires binding of the DEP domain to the third intracellular loop of the receptor. Recent studies identified the dynamic intramolecular interaction between the Gbeta(5) and DEP domains, which suggested that the Gbeta(5)-RGS7 dimer could alternate between the "open" and "closed" conformations. Here, we identified point mutations that weaken DEP-Gbeta(5) binding, presumably stabilizing the open state, and tested their effects on the interaction of Gbeta(5)-RGS7 with the M3R. We found that these mutations facilitated binding of Gbeta(5)-RGS7 to the recombinant third intracellular loop of the M3R but did not enhance its ability to inhibit M3R-mediated Ca(2+) mobilization. This led us to the idea that the M3R can effectively induce the Gbeta(5)-RGS7 dimer to open; such a mechanism would require a region of the receptor distinct from the third loop. Indeed, we found that the C-terminus of M3R interacts with Gbeta(5)-RGS7. Truncation of the C-terminus rendered the M3R insensitive to inhibition by wild-type Gbeta(5)-RGS7; however, the open mutant of Gbeta(5)-RGS7 was able to inhibit signaling by the truncated M3R. The GST fusion of the M3R C-tail could not bind to wild-type Gbeta(5)-RGS7 but could associate with its open mutant as well as with the separated recombinant DEP domain or Gbeta(5). Taken together, our data are consistent with the following model: interaction of the M3R with Gbeta(5)-RGS7 causes the DEP domain and Gbeta(5) to dissociate from each other and bind to the C-tail, and the DEP domain also binds to the third loop, thereby inhibiting M3R-mediated signaling.
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Affiliation(s)
- Simone L Sandiford
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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Sandiford SL, Slepak VZ. The Gbeta5-RGS7 complex selectively inhibits muscarinic M3 receptor signaling via the interaction between the third intracellular loop of the receptor and the DEP domain of RGS7. Biochemistry 2009; 48:2282-9. [PMID: 19182865 DOI: 10.1021/bi801989c] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Regulators of G protein signaling (RGS) make up a diverse family primarily known as GTPase-activating proteins (GAPs) for heterotrimeric G proteins. In addition to the RGS domain, which is responsible for GAP activity, most RGS proteins contain other distinct structural motifs. For example, members of the R7 family of RGS proteins contain a DEP, GGL, and novel DHEX domain and are obligatory dimers with G protein beta subunit Gbeta5. Here we show that the Gbeta5-RGS7 complex can inhibit Ca2+ mobilization elicited by muscarinic acetylcholine receptor type 3 (M3R), but not by other Gq-coupled receptors such as M1, M5, histamine H1, and GNRH receptors. The isolated DEP domain of RGS7 is sufficient for the inhibition of M3R signaling, whereas the deletion of the DEP domain renders the Gbeta5-RGS7 complex ineffective. Deletion of a portion of the third intracellular loop allowed the receptor (M3R-short) to signal but rendered it insensitive to the effect of the Gbeta5-RGS7 complex. Accordingly, the recombinant DEP domain bound in vitro to the GST-fused i3 loop of the M3R. These results identify a novel molecular mechanism that can impart receptor subtype selectivity on signal transduction via Gq-coupled muscarinic receptors.
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Affiliation(s)
- Simone L Sandiford
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami School of Medicine, 1600 NW 10 Avenue, R-189, Miami, Florida 33136, USA
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Detection of PBDE effects on mRNA expression in chicken (Gallus domesticus) neuronal cells using real-time RT-PCR and a new differential display method. Toxicol In Vitro 2008; 22:1337-43. [DOI: 10.1016/j.tiv.2008.03.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 02/05/2008] [Accepted: 03/25/2008] [Indexed: 11/23/2022]
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Hashimoto Y, Morisawa K, Saito H, Jojima E, Yoshida N, Haga T. Muscarinic M4 receptor recycling requires a motif in the third intracellular loop. J Pharmacol Exp Ther 2008; 325:947-53. [PMID: 18337477 DOI: 10.1124/jpet.107.135095] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study was performed to identify sequence(s) in the third intracellular loop (i3) of the muscarinic acetylcholine receptor M4 subtype (M4 receptor) involved in its internalization and recycling. In transiently transfected human embryonic kidney 293-tsA201 cells, 40 to 50% of cell-surface M4 receptors are internalized in an agonist-dependent manner, and approximately 65% of internalized receptors are recycled back to the cell surface after removal of the agonist. We examined the internalization and recycling of M4 receptor mutants with partial deletion in i3 and found that various mutants (M4del-K(235)-K(240), M4del-T(241)-K(271), and M4del-W(339)-N(372)) showed internalization and cell-surface recycling in a similar manner to the M4 receptor. We also found that the mutant M4del-L(272)-R(338) was internalized to only half the extent of the M4 receptor and was recycled after agonist removal, and the mutant M4del-V(373)-A(393) was also internalized to half the extent of the wild type but was not recycled back to the cell surface after agonist removal. When the sequence corresponding to Val(373)-Ala(393) was grafted onto the i3 portion of a recycling-negative mutant of muscarinic M2 receptor with deletion of almost the whole of the i3 sequence, approximately 40% of the chimeric receptor on the cell surface was internalized, and more than 65% of the internalized receptors were recycled back to the cell surface. These results indicate that the regions including Leu(272)-Arg(338) and Val(373)-Ala(393) are involved in internalization of the M4 receptor, and the region including Val(373)-Ala(393) is indispensable for its recycling, whereas the other regions of i3 are dispensable for internalization and recycling.
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Affiliation(s)
- Yuichi Hashimoto
- Institute for Biomolecular Science, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan.
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